Lawyers for leading Zimbabwean human rights activists and political detainees abducted by the state, held incommunicado for weeks and then imprisoned in defiance of a court order have accused the police of torturing them in an attempt to extract false confessions of a plot against President Robert Mugabe.

The lawyers are demanding the release of Jestina Mukoko, one of the country's most prominent activists and head of the Zimbabwe Peace Project, and eight others who were jailed on Christmas Eve despite a judge ruling that they should be moved to hospital and examined by doctors for signs of torture.

"The state is in contempt of court," said Alec Muchadehama, one of the lawyers for the detainees. "The reason they brought some of them to court is for public relations purposes to save their image but the truth is that they have no intention of releasing them. The police have not moved an inch and our clients are still detained at Chikurubi maximum security prison, including [a] two-year-old child."

Mukoko was taken from her home by armed men on 3 December. Five days later, Police Chief Superintendent T Nzombe wrote to the national NGO coalition saying Mukoko was not in police custody and that the state regarded her disappearance as a "kidnapping".

But Mukoko and eight others were suddenly brought to court on Christmas Eve, when it was revealed that they had been in police custody all along. They were accused of being part of a plot to train an armed group in Botswana to attack Zimbabwe and remove Mugabe from power.

The government and state-run media has made much of the supposed plot in recent weeks but produced no firm evidence.

Last week, South Africa's president, Kgalema Motlanthe, said the Zimbabwean government had raised the accusations at regional meetings but "we never believed" it.